Power Grids
FIGS. 1-4 illustrate related art disclosed in U.S. Pat. No. 8,002,592. FIG. 1 shows a transmission tower 200 which is used to suspend power transmission lines 202 above the ground. The tower 200 has cantilevered arms 204. Insulators 206 extend down from the arms 204. One or more suspension clamps 208 are located at the bottom ends of the insulators 206. The lines 202 are connected to the suspension clamps. The clamps 208 hold the power transmission lines 202 onto the insulator 206.
FIGS. 2-4 illustrate an example of a suspension clamp 208, which generally comprises an upper section 210 and a lower support section 212. These two sections 210, 212 each contain a body 214, 216 which form a suspension case. The bodies 214, 216 each comprise a longitudinal trough (or conductor receiving area) 215, 217 that allow the transmission conductor 202 to be securely seated within the two sections when the two sections are bolted (or fastened) together by threaded fasteners 201 (not shown). This encases the transmission conductor 202 between the two bodies to securely contain the transmission conductor 202 on the clamp 208. Threaded fasteners are not required and any other suitable fastening configuration may be provided.
The two bodies 214, 216 connected together are suspended via a metal bracket 218 that attaches to the lower body 216 at points via bolt hardware 220.
The lower body, or lower body section, 216 comprise a first end 219 and a second end 221. The conductor receiving area (or conductor contact surface) 217 extends from the first end 219 to the second end 221 along a top side of the lower body 216. The conductor receiving area, including longitudinal trough 217, forms a lower groove portion for contacting a lower half of the conductor 202. A general groove shape is not required, and any suitable configuration may be provided.
In one implementation, the upper and lower sections 210, 212 each have embedded within their respective bodies 214, 216 one-half of a current transformer 222, 224 that is commonly referred to in the industry as a split core current transformer. When these components 222, 224 are joined, they form an electromagnetic circuit that allows, in some applications, the sensing of current passing through the conductor 202. In one implementation, the current transformer is used for power sensing, data collection, data analysis and data formatting devices. In some implementations the current transformer may be located outside of the clamp or similar device or, in some implementations, power may be provided by another means.
The body 214 of the upper section 210 contains a first member 232 and a second member 234 forming a cover plate. The first member 232 comprises a first end 233, a second end 235, and a middle section 237 between the first end 233 and the second end 235. The conductor receiving area (or conductor contact surface) 215 extends from the first end 233 to the second end 235 along a bottom side of the first member 232. The conductor receiving area 215 forms an upper groove portion for contacting an upper half of the conductor 202. A general groove shape is not required, and any suitable configuration may be provided. In one implementation, the first member 232 further comprises a recessed cavity 226 at the middle section 237 that effectively contains an electronic circuit 228. In this implementation, the electronic circuit 228 is designed to accept inputs from several sensing components. This cavity 226 may be surrounded by a faraday cage 230 to effectively nullify the effects of high voltage EMF influence from the conductor 202 on the circuitry 228. The faraday cage may also surround the current transformer 222. The cover plate, or cover plate member, 234 can cover the top opening to the cavity 226 to retain the electronic circuit inside the body, or upper body section, 214. The electronics may be housed in a metal or plastic container, surrounded by the noted faraday cage, and the entire assembly can be potted, such as with epoxy for example.
The electronic circuit 228 can accept and quantify in a meaningful manner various inputs for monitoring various parameters of the conductor 202 and the surrounding environment. The inputs can also be derived from externally mounted electronic referencing devices/components. The inputs can include, for example: Line Current reference (as derived from the Current transformer 222, 224 or other means); Barometric pressure and Temperature references—internal and ambient (as derived from internal and external thermocouples 236, 238 or other means); Vibration references of the conductor (as derived from the accelerometer 240, such as a 0.1-128 Hz sensor, for example, or other means); and Optical references (as derived from the photo transistor 242 in a fiber optic tube or other means). The optical reference portion may, for example, allow the clamp to look up and see flashes of light from corona if the insulator starts to fail, or lightening indication storm activity, and/or tensile references (as derived from the tension strain device 244 which may be included in certain implementations). The tensile references from the tensile indicators 244 may, for example, provide information indicating that ice is forming as the weight of the conductor increases due to ice build up.
Supervisory Control And Data Acquisition (SCADA) generally refers to an industrial control system such as a computer system monitoring and controlling a process. Information derived by the electrical/electronic circuitry can exit the circuit 228 via a non-conductive fiber optic cable 246 and be provided up and over to the transmission tower 200 and ultimately at the base of the tower and fed into the user's SCADA system to allow the end user to access and view electrical and environmental conditions at that sight, or the information can be transmitted to a remote or central site. The suspension clamp or other sensing device may be alternatively configured to wirelessly transmit information from the electronic circuit 228 to a receiver system.
Problems Associated with Corona and Conventional Corona Detection Systems
Corona is a type of electrical discharge which will corrode or eat away at wire, insulators, and anything else in the vicinity. Conventional methods of corona detection involve ultraviolet and ultrasonic detection. Both suffer from a high cost of implementation and various disadvantages. For example, power lines can generate corona that can be seen by using special cameras operating in the ultraviolet spectrum. However, such cameras are large and expensive. The cameras are generally sent to places where an insulator appears to be eaten away, but may not be effective since corona can be intermittent and is affected by many environmental conditions such as moisture and air pressure. Further, conventional ultraviolet detectors require a user to manually operate a device and aim at an area suspected to contain corona. As such, these detectors are cumbersome and not autonomous. Furthermore, conventional ultrasonic detectors employ nondiscriminatory means of detecting corona, seeking any noise in a given ultrasonic frequency range. Thus, these detectors are often not sufficiently accurate.
Repair or Servicing a Transmission Line
Initially, one must locate where a power transmission line is broken. However, power transmission lines can run hundreds of miles between substations, and the only information generally available is that one substation is supplying power and the next one is not receiving the supplied power. Accessibility to power transmission lines may vary. In some cases, the power transmission lines may be accessible by motorized ground vehicles. In other cases, lines may only be accessible by helicopter, wherein a service technician must hang under the helicopter to service or repair a line. Such repairs or maintenance can be very expensive. Accordingly, preventative methods of detecting problems such as corona are needed.
Conventional Communication Protocols
In order to retrieve information about the system, rapid and secure communication is necessary. Radio communication via Ethernet is one option. However, organizing an Ethernet network requires the use of devices known as routers or switches. Each router or switch will look at an Ethernet packet of information and make note of the source address and the destination address as the packet arrives at a port. If the destination is known, the packet is forwarded to only one port which is known to be connected to that destination device. If it is not a known address, it is repeated to all ports except the port where it arrived. When the destination device responds, the source address will appear in a packet on a single port which permit the router or switch to learn where to send the next packet with that particular destination address.
There are specific protocols which optimize the route for delivering a packet and to remove the opportunity for a packet to become repeated in a loop in the network. Some of the more common protocols are Spanning Tree Protocol and Rapid Spanning Tree Protocol. A popular radio protocol for packet-based transmission is Zigbee which is described in standard IEEE 802.15.4, but it is only useful in networks in a small geographic area.
There is a need for accurate, inexpensive, small and easy-to-implement systems and methods for detecting corona. These may allow for fast analysis of any actual or potential repair problems and power optimization capabilities along transmission lines, with lower costs of repair, better preventative maintenance, and faster restore times. A need also exists for a way of collecting and communicating data by a widespread installation of sensing devices such as corona sensors over large geographic areas (such as power line grids).